Voltage regulating system



July 2, 1968 J. FRENCH 3,391,331

VOLTAGE REGULATING SYSTEM Filed Oct. 14, 1964 5 Sheets-Sheet INVENTORJOHN F. FRENCH Emu 56. Watt y 1968 J. F. FRENCH 3,391,331

VOLTAGE REGULATING SYSTEM Filed Oct. 14. 1964 3 Sheets-Sheet z INVENTOQJOHN F. FRENCH 3 Sheets-Sheet 5 Filed Oct. 14, 1964 INVENTOR.

JOHN F. FRENCH 5% may N Em United States Patent 3,391,331 VOLTAGEREGULATING SYSTEM John F. French, Aurora, [1]., assignor to EdwardDavis, Chicago, Ill. Filed Oct. 14, 1964, Ser. No. 403,759 Claims. (Cl.323-22) ABSTRACT OF THE DISCLOSURE A voltage regulating system includinga control circuit for a silicon controlled rectifier which is connectedbetween an AC power source and the primary winding of a powertransformer. The control circuit fires the silicon controlled rectifierat progressively sooner intervals during successive half-cycles of theAC source to increase the transformers power capabilities in successivestages beyond its rated capacity, by minimizing its subjection to severemechanical shock.

The present invention relates to improvements in machines for stressrelieving wire coil springs and is more particularly concerned with thenovel construction and assembly of such machine and the electricalcontrol therefor.

More specifically, the invention is concerned with a stress relievingattachment for spring coiling machines, particularly of the type usedfor coiling pig-tail springs, and it includes novel means to receivecoiled springs in rapid succession directly from the forming machine andclamping them in a position to be engaged at opposite ends by electrodeswhich supply electric current thereto for predetermined periods of timeand to thereafter dischange said springs. The electrodes have associatedwith them novel means to insure dissipation of heat generated. The clampand electrodes are readily adjustable to adapt the machine for heattreating springs of various diameters and length.

It is therefore an object of the invention to automaticallystress-relieve coiled springs by resistance heating in their normalpassage through the forming machine.

Another object is to automatically provide means for accurate control ofthe stress-relieving temperature achieved as a function of resistanceheating.

Another object is to control the stress-relieving current by the use ofa silicon controlled rectifier.

Another object is to provide means whereby the electrodes are kept cool.

Another object is to provide finished springs of constant and uniformdimensions.

Another object is to provide novel means to freely adjust the electrodesso as to provide new wearing surfaces to the spring as required.

Another object is to provide electronic control circuitry which ismodular in design so as to be serviced when necessary by an individualwithout advanced electronic training.

Another object is to provide means of controlling primary line currentby means. of closed loop feedback.

Another object is to provide novel clamp jaw assemblies whereby eachclamping assembly and associated electrode is independently adjustablewith respect to the other to adapt them to accommodate any configurationof spring which the basic machine is capable of forming.

Another object is to provide means whereby accessory controls, such asoptical pyrometers, may be used to control stress-relieving temperaturewith extreme accuracy.

Another object is to provide a stress-relieving attachment for springcoiling machines.

Another object is to provide novel means and apparatus forstress-relieving pig-tail springs.

3,391,331 Patented July 2, 1968 "ice brAnother object is to providenovel clamp jaw assem- 1es.

The structure by means of which the above noted and other advantages andobjects of the invention are attained will be described in the followingspecification, taken in conjunction with the accompanying drawings,showing a preferred illustrative embodiment of the invention, in which:

FIG. 1 is a front elevational view of the stress-relieving attachment.

FIG. 2 is a side elevational view as viewed along line 22 of FIG. 1.

FIG. 3 is an enlarged sectional view, taken along line 33 of FIG. 2.

FIG. 4 is a schematic of the electric wiring.

Referring now to the exemplary disclosure of the invention shown in theaccompanying drawings, and particularly in FIG. 1, the springs areformed in a machine of conventional construction which includes a feedclamp arm 11 journalled at 12 and into which a newly formed spring A isadvanced. At a select cycle of operation, the feed clamp arm rocks in acounterclockwise direction to carry the spring upwardly through an aresubstantially into the position occupied by spring B. When the spring isin the B position, it is engaged near its ends by novel pneumaticallyoperated clamp mechanisms 13 and 14 each of which has associated withit, as better explained hereinafter, an electrode adapted to receiveelectric C1111- rent, at predetermined intervals and for a predeterminedperiod of time, for passage through the spring and heating same. Theclamp-electrode assemblies are mounted in a frame structure thatincludes an upstanding support plate 15 that is attached firmly, as at16, to the frame of the spring forming machine (not shown). Thisassembly is operated in conjunction with operation of the spring formingmachine so that each time a spring is formed, and this occurs with greatrapidity, the formed spring is thrust forward into the feed clamp arm 11which then carries it to the electrode-clamp assemblies whichimmediately function to heat the spring which is then discharged onto aconveyor track 17 or other means for conveying the stress-relievedspring away from the machine.

Referring specifically to FIGS. 2 and 3, which depict theelectrode-clamp means 13 for engaging the knotted end of the spring B,said means includes an aluminum block 18 that is secured firmly to theplate 15 and has a plurality of heat dissipating fins 19 on its frontface. A pneumatic piston-cylinder assembly 21, having an air lineconnected at each end, as at 22, 23, is secured firmly to the back faceof block 18 and its piston rod 24 extends freely through said block. Aclamp arm 25, pivoted on said block at 26, has its upper end pivotallyattached to said piston rod, as at 27, and its other or depending end isoffset rearwardly to provide a clamp jaw 28. This jaw, when in clampingposition engages with the base or knotted end of the coil spring B andclamps it firmly against an electrode 29 mounted for adjustment and easyreplacement in the block 18. Although the electrode may be mounted inany convenient manner it preferably seats in a slot 30 in said block andis held firmly in an adjusted position as by screws 31.

Obviously, the clamp is moved into and out of clamping position by theadmittance of air pressure into the respective ends of cylinder 21. Suchair flow is electrically controlled and is cycled tothe machine cycle.As more fully explained hereinafter, it is timed to clamp the springprior to flowing electric current to the electrode and to release thespring after the current flow to the electrode has been cut off. Thisprevents the formation of an electric are at the point of contact of thespring with the electrode.

The tail end of spring B is, simultaneously to engagement of clamp jaw23 with the knotted end of the spring, clamped in the electrode-clampmeans 14, located on the front side of the machine. This means is bestshown in FIG. 2 and it comprises an aluminum block 32 having heatdissipating fins 33 on its upper face. The block is secured firmly to awall 34 of insulation material that is connected firmly to and held inplace by a cross bar 35 supported in spaced relation from plate 15, asby means of tie rods 36. The wall 34 can be adjusted vertically,horizontally and laterally to accommodate springs of various diameters.

Mounted firmly on the bottom face of block 32 is a pneumaticpiston-cylinder assembly 37 having connection at each end with a sourceof air pressure through conduits 38. A piston rod 39 extends out of saidassembly and it is pivotally connected, as at 41, to a clamp knuckle 42.This knuckle has an arcua'te rack 43 concentric with said pivot 41,which is meshed with a rack 44 on the bottom face of block 32. Theknuckle includes a clamp jaw 45 disposed, when in one position, toengage over and clamp the tail end of spring B firmly against anelectrode 46 carried by block 32. In operation, to move the clamp jaw 45out of engagement with the spring, the piston rod is drawn into thecylinder. This rotates the knuckle about its pivot 41 into substantiallythe dotted line position shown. It should be noted that the knuckle issuch that it is withdrawn clear of the spring end when in unclampedposition. Movement of the knuckle into clamping and unclamping positionsis cycled so as to clamp and unclamp the spring prior to and after,respectively, current is supplied to the electrode so as to preventelectric arcing.

In FIG. 4, a circuit incorporating the principles of the presentinvention for stress relieving heavy wire coils is indicated generallyby the reference character 47. The circuit 47 includes the leads L1, L2,and L3 with the leads L1 and L2 connected to a 230 v., 100 amp AC supplyand lead L3 serving as a neutral.

Lead L1 extends to one terminal of the primary of a stress relieftransformer T1, whose secondary is connected to the pair of electrodes29 and 46. As stated, the electrodes 29 and 46 are adapted to be clampedto opposite ends of the coil B, which is to be stress relieved, afterthe coil is formed. Since this transformer T1 must draw considerablepower and is subject to considerable heat, a fan 48 connected betweenleads L1 and L3 is provided to cool the transformer and a thermistor THlis provided for temperature sensing of the transformer condition. Ameter M1 is connected across the primary of transformer T1.

The other terminal of transformer T1 is connected to the anode of asilicon controlled rectifier SCRl through a positively poled rectifieror diode D1 and is also connected to the cathode of SCRl through anegatively poled diode D2. The anode of SCRl and the negative pole ofdiode D1 are also connected to lead L2 through a positively poled diodeD3, while the cathode of SCR1 and the positive terminal of diode D2 areconnected to lead L2 through a positively poled diode D4. The diodes orunidirectional circuit elements D1, D2, D3 and D4 are thus connected ina rectifier bridge arrangement in which current cannot flow between theend terminals and leads L1 and L2 unless SCRI is fired. The SCRItherefore serves as a gate for the transformer T1.

A pair of controlled avalanche silicon rectifiers CASR1 and CASR2 areconnected between leads L1 and L2 to protect the diodes D1, D2, D3 andD4 together with SCRl from transients appearing across the lines. Thesilicon controlled rectifier SCRI has a control electrode E3 and ittogether with the cathode of SCRl are connected to the output of a gatecircuit indicated generally at G1.

The gate circuit G1 is controlled during each successive half cycle ofAC current on lead L1 as will be explained. The gate circuit G1 enablesSCR1 to fire for passing current through the primary of transformer T1and thereby enable stress relief of the coil connected across electrodes29 and 46.

Thus, lead L1 also extends through normally closed form C contacts Klaof an alarm relay Kl to one terminal of the normally open contacts S1controlled by a cam C1. A lamp PL1 connected between the normally closedcontacts Kla and lead L3 serves to indicate contacts Kla are closed. Theother terminal of contacts S1 extend through the primary of atransformer T2 to lead L3. Transformer T2 is adapted to supply power togate circuit G1.

In addition, lead L1 extends to one terminal of normally open contactsS2 which are under control of a second cam C2. The other termnial ofcontacts S2 is connected through a solenoid SR1 to the neutral lead L3.Cams C1 and C2 are adapted to be operated together for closing switchesS1 and S2, when the machine has completed its coil forming operation ona wire segment and the coil is positioned at the stress relief stationbetween electrodes 29 and 46. Solenoid SR1 operates at that time tocause electrodes 29 and 46 to be clamped to opposite ends of the coil.

The output of transformer T2 is approximately 35 v., for example, and isapplied to a rectifier bridge R31 in gate circuit G1. The positiveoutput terminal of bridge RBI is connected through a 3.3K resistor R1and diode D5 over a lead L6 to one terminal of a potentiometer P1 andthe negative output is connected to a lead L7. The gate circuit G1 alsoincludes a transistor TR1 whose emitter circuit is connected to lead L6through a 432 ohm resistor R2 and to lead L7 through a 22K resistor R3.The base circuit of transistor TRl is connected to a 60K resistor R4 tothe arm of potentiometer P1 and a 200 t. capacitor Cla connects thejunction of the potentiometer arm and resistor R4 to lead L6. The otherterminal of potentiometer P1 is connected through a 4.7K resistor R5 tolead L7. Thus adjustment of the potentiometer P1 serves to control theRC time constant of the potential applied to the base circuit oftransistor TR1 which may be, for example, a 2N525.

The collector circuit of transistor TR1 is connected to the emitter of aunijunction transistor UT1 whose base circuits are respectivelyconnected through a ohm resistor R7 to the junction of resistor R1 anddiode D5 and through the primary of an output pulse transformer T3 and a22 ohm resistor R8 to lead L7. A clamp diode D7 is connected in shuntwith transformer T3, transistor UT1 and resistors R7 and R8. Thejunction of the emitter circuit of UT1 and the collector circuit of TRlis also connected to one terminal of a .22 ,uf. capacitor C2a whoseother terminal is connected to lead L7.

Thus transistor UT1 conducts or fires when the positive bias on itsemitter circuit exceeds its stand-off ratio, and this in turn depends onthe time period in which capacitor C2a is charged to this value. Thetime period for the charge on capacitor GM to increase varies inproportion to the conduction of transistor TRI. The conduction of TR1 inturn depends on the RC constant of potentiometer P1 and capacitor Cla.Therefore, the points at which UT1 conducts during each half-cycle of ACapplied to bridge RBI occurs at a progressively suitable interval ascapacitor Cla charges to progressively higher values. This point istherefore determined by the setting of potentiometer P1 which may bemanually adjusted to secure a desired output from transformer T1.

The output of transformer T3 is connected over leads L4 and L5 acrossthe control electrode and cathode of SCR1 for firing the SCR. The SCRltherefore fires at a progressively shorter interval after the start orintiation of each successive half cycle applied to gate circuit G1 dueto the decreasing time necessary to charge capacitor C2a to the standoff ratio.

Thus, the transformer T1 is enabled to withstand peak power loads ofmany times its rated value. For example, over a 20 kva. input may beapplied to the transformer T1 rated at 5 kva., as these loads areapplied intermittently while the mechanical shock resulting from theapplication of the loads is minimized during the successive cyclesinstead of being instantaneously applied.

The thermistor THl has one terminal connected through relay K1 to thenegative output terminal of a rectifier bridge RB2. The positive outputterminal of rectifier bridge RB2 is connected through a 1K resistor R9and an adjustable resistor R10 to the other terminal of transistor TH1.Input power to the bridge RBZ is supplied by a 12 volt outputtransformer T4 whose primary is connected between leads L1 and L3.

Thus, if transformer T1 becomes overheated this is detected by a changein the voltage drop across THl, which enables relay K1 to operatecontacts Kla. When contacts Kla switch, lamp PL1 is extinguished.Transformer T2 is simultaneously deenergized to prevent the gate circuitG1 from enabling energization of transformer T1 while lamp PL2 islighted to signal this condition. Other alarm features may include apyrometer or other temperature sensing element for monitoring the springtemperature.

As each coil is completed and is positioned at the stress reliefstation, the cams C1 and C2 operate to close contacts S1 and S2respectively. Contacts S2 on closing connect solenoid SR1 across leadsL1 and L3 and the solenoid energizes to clamp the electrodes 29 and 46to opposite ends of the coil B. The transformer T1 however, does notpass current, since the SCRl is extinguished.

Simultaneously, contacts S1 on closing energizes the primary oftransformer T2 and it supplies approximately 35 v. through the bridgerectifier RBI to the gate circuit G1. Capacitor Cla therefore starts tocharge in a positive direction and positive potential is thereaftersupplied to the emitter circuit of transistor TRl. The base circuit oftransistor TR1 starts to swing positive at a rate dependent on the RCtime constant of capacitor C1a and potentiometer P1 and it conductsafter the start of the power cycle applied to lead L1.

As the base of transistor TR1 starts to swing positive, it conducts at aheavier rate to charge capacitor C2a in a positive direction. Thiscauses UT1 to fire. As this occurs, the transformer T3 provides anoutput pulse to fire SCRl and transformer T1 therefore receives itsfirst power pulse considerably after the start of the correspondingcycle applied across leads L1 and L2.

Between cycles capacitor C2a is effectively discharged. The voltage oncapacitor Cla increases to progressively higher levels on each halfcycle since its RC time constant is larger and it cannot dischargecompletely during each successive cycle. Therefore, on each successivehalf cycle TRl will conduct more heavily to charge C2a more rapidly to alevel sufiicient to fire UT1 at progressively shorter intervals at eachhalf cycle. The SCR1 is therefore fired at correspondingly soonerintervals so that transformer T1 is gradually brought into peak powerdelivery.

After a predetermined interval cams C1 and C2 open contacts S1 and S2 todeenergize the gate circuit G1 and solenoid SR1. SCR1 therefore, remainextinguished until the next coil is brought into position for clampingwhile the stress relieved coil is passed to the succeeding station.

Although I have described a preferred embodiment of my invention, inconsiderable detail, it will be understood that the description thereofis intended to be illustrative, rather than restrictive, as many detailsof the strucure and circuitry disclosed may be modified or changedwithout departing from the spirit or scope of the invention.Accordingly, I do not desire to be restricted to the exact constructiondescribed.

I claim:

1. A circuit for energizing a transformer whose primary is connectedbetween a pair of leads adapted to provide power substantially in excessof the rated capacity of said transformer to enable stress relief of ametal coil, the improvement comprising a normally closed gate connectedbetween one of said leads and said primary and normally preventingcurrent flow through said primary, and means controlled responsive tosuccessive half cycles of AC current appearing on the other of saidleads for opening said gate at progressively shorter intervals afterinitiation of each half cycle whereby the power applied to saidtransformer is increased in successive stages.

2. In the circuit claimed in claim 1, means operatively connected to thegate opening means for enabling opening thereof only during thepositioning of a load across the output of said transformer.

3. In the circuit claimed in claim 1, a temperature sensing element forsensing the heat rise in said transformer, and means connected to saidgate opening means for preventing opening thereof upon said temperaturerising above a predetermined level.

4. The circuit claimed in claim 1, in which said means comprise anamplifying device having a control electrode controlled in response tothe appearance of each successive half cycle for causing said amplifyingdevice to conduct at progressively higher levels and in which said gatecomprises a silicon controlled rectifier having a control electrodecoupled to the output of said amplifying device.

5. The circuit claimed in claim 1, in which said means comprises anadjustable RC circuit adapted to be energized on each of said successivehalf cycles, a capacitor, an electronic valve controlled by said RCcircuit to charge said capacitor at progressively shorter time intervalsafter initiation of each successive half cycle.

6. A circuit for energizing a transformer whose primary is connectedbetween a pair of leads adapted to provide power substantially in excessof the rated capacity of said transformer to enable stress relief of ametal segment, the improvement comprising a normally closed gateconnected to said primary and normally preventing current flow throughsaid primary, and means controlled responsive to AC current appearing onone of said leads for opening said gate at progressively shorterintervals after initiation of respective half cycles of AC currentwhereby the power applied to said transformer is increased in successivestages.

7. A circuit for energizing a transformer having a primary connectedbetween a pair of leads adapted to provide power substantially in excessof the rated capacity of said transformer for stress relief of a metalstrip, the improvement comprising a silicon controlled rectifierconnected between one of said leads and said primary and normallyextinguished for preventing current flow through said primary, means forpassing current only in response to each successive AC cycle appearingon the other of said leads, including a transistor having base, emitterand collector circuits, means rendering said transistor conductive athigher conduction rates after the start of each successive cycle, acapacitor connected in series with said emitter and collector circuitsand adapted to be charged thereby at progressively shorter intervals,means responsive to a predetermined charge level on said capacitor forfiring said silicon controlled rectifier at progressively shorterintervals after the initiation of each successive cycle, whereby thepower applied to said transformer is increased in successive stages, andmeans for enabling the energization of said current passing means onlyduring the positioning of a load across the output of said transformer.

8. A circuit for energizing a transformer having a primary connectedbetween a pair of leads adapted to provide power at least several timesgreater than the rated capacity of said transformer for stress relief ofa metal strip, the improvement comprising a rectifier bridge having endterminals of each leg connected between one of said leads and saidprimary and adapted to prevent the flow of current therebetween alongany one leg, a normally extinguished silicon controlled rectifierconnected across the legs of said bridge and enabling the passage ofcurrent from either of said leads to the other lead and through saidprimary only when said silicon controlled rectifier is fired, means forderiving a DC potential during successive half cycles of A.C. appearingon the other of said leads, means adapted to conduct current on thederivation of said DC. potential at a level dependent on the level ofthe biasing potential applied thereto, a capacitor connected to saidcurrent conducting means adapted to be charged to suecessively higherlevels on each of said successive half cycles for raising said biasingpotential accordingly, and means interconnecting the output of saidconductive means with the control electrode circuit of said siliconcontrolled rectifier whereby said silicon controlled rectifier is causedto fire at progressively shorter intervals after the initiation of eachalternate half cycle applied to said rectifier bridge whereby the powerapplied to said transformer is increased in successive stages.

9. A circuit for energizing a transformer whose primary is connectedbetween a pair of leads adapted to supply power to said primarysubstantially greater than the power rating of said transformer forenabling the stress relief of a metal coil adapted to be connectedacross the secondary of said transformer, the improvement comprising asilicon controlled rectifier having a control electrode and connectedbetween one of said leads and said primary and normally preventingcurrent fiow between said leads and through said primary, a rectifierarrangement connected across said Silicon controlled rectifier forenabling the passage of current from either of said leads to the otherlead and through said primary only when said silicon controlledrectifier is fired, means for deriving a DC). potential duringsuccessive half cycles of A.C. appearing on the other of said leads, atransistor having base, emitter and collector circuits with said emitterand collector circuits connected across said means, a capacitorconnected across said transistor base and emitter adapted to be chargedto progressively higher levels on each successive A.C. half cycle forcontrolling the conduction level of said transistor accordingly, aunijunction transistor having base circuits connected across said meansand an emitter circuit connected to the collector circuit of said onetransistor, and adapted to be fired at progressively sooner intervals inresponse to the conduction level of said transistor, meansinterconnecting one of said unijunction base circuits with said controlelectrode of said silicon controlled rectifier whereby said siliconcontrolled rectifier is caused to fire at progressively sooner intervalsduring each successive half cycle applied to said rectifier bridgewhereby the power applied to said transformer is increased in successivestages.

10. A circuit for energizing a 5 kva. transformer having a primaryadapted to be connected across a pair of leads arranged to supply atleast 20 kva. for enabling said transformer to stress relieve a metalcoil, the improvement comprising a silicon controlled rectifier having acontrol electrode and connected between one of said leads and saidprimary and normally preventing current flow between said leads andthrough said primary, a rectifier arrangement connected across saidsilicon controlled rectifier for enabling the passage of current fromeither of said leads to the other lead and through said primary onlywhen said silicon controlled rectifier is fired, a rectifier bridgeadapted to derive a DC. potential during successive half cycles of A.C.appearing on the other of said leads, a plurality of resistors connectedacross said bridge, one transistor having base, emitter and collectorcircuits with said emitter circuit connected to one terminal of saidbridge through a junction between said plurality of resistors, aunijunction transistor having base circuits connected across said bridgeand an emitter circuit connected to the collector circuit of saidtransistor, a capacitor connected between said collector circuit andanother terminal of said bridge, an adjustable RC circuit connectedacross said bridge and to the base circuit of said one transistor forcontrolling the conduction of said one transistor whereby the charge onsaid capacitor is caused to reach a predetermined value at aprogressively sooner interval in each successive half cycle appearing onsaid one lead, means interconnecting one of said unijunction basecircuits with the control electrode of said silicon controlled rectifierwhereby said silicon controlled rectifier is caused to fire atprogressively shorter intervals during each successive half cycleapplied to said rectifier bridge whereby the power applied to saidtransformer is increased in successive stages, and means for enablingsaid bridge to supply said D.C. only during the positioning of a loadacross the secondary of said transformer.

References Cited UNITED STATES PATENTS 2,623,168 12/1952 Stadum et al.2l9-50 X 2,739,281 3/ 1956 Rockafellow 323-18 3,036,260 5/1962 Berweger32318 X 3,275,802 9/1966 Vandivere et al 219-499 3,307,093 2/1967 Wright3l8-227 X JOHN F. COUCH, Primary Examiner. W. E. RAY, Examiner.

